The reliability of shear elastic modulus measurement of the ankle plantar flexion muscles is higher at dorsiflexed position of the ankle

Absolute reliability of Young's modulus of the soleus muscle and Achilles tendon measured using shear wave elastography in healthy young males

Background

Stiffness of the soleus muscle (SOL) and Achilles tendon (AT) are associated with Achilles tendinitis and medial tibial stress syndrome. Therefore, reliable SOL and AT stiffness measurements are important for monitoring clinical progress. However, little is known about the absolute reliability of the stiffness measurements of SOL and AT in different ankle positions. This study aimed to determine the absolute reliability of the Young's modulus measurements of the SOL and AT in different ankle positions in healthy young males.

Methods

This study included 33 healthy young males. SOL and AT stiffnesses were measured using Young's modulus and shear-wave elastography (SWE). Measurements were taken while the participants were kneeling, with their knees flexed to 90°, and the upper body supported by a table. Ultrasound images were recorded at ankle dorsiflexion angles of -10°, 0°, and 10°. The same measurements were repeated 15 min after the first measurement. Bland-Altman plots were used to verify the type or amount of error and 95 % confidence interval of the minimal detectable change (MDC95) values of the measurements.

Results

Bland-Altman plots identified that there was no fixed or proportional bias and that there was good agreement between the first- and second-time measurements of the SOL and AT, respectively, among all angles. The MDC95 of the Young's modulus of SOL at -10°, 0°, and 10° of ankle dorsiflexion were 5.6 kPa, 7.0 kPa, and 10.1 kPa, respectively, and AT were 15.8 kPa, 16.4 kPa, and 17.8 kPa, respectively.

Conclusion

Young's modulus measurements of the SOL and AT using SWE can be used to quantify elastic properties with high confidence. Clinically, assessing changes in the Young's moduli of the SOL and AT using SWE may help determine the effectiveness of interventions.

Reliability of lower leg muscle elasticity using shear wave elastography in non-weight-bearing and weight-bearing

PURPOSE

Muscle elasticity can be quantified with shear wave elastography (SWE) and has been used as an estimate of muscle force but reliability has not been established for lower leg muscles. The purpose of this study was to examine the intra-rater and inter-rater reliability of elasticity measures in non-weight-bearing (NWB) and weight-bearing (WB) for the tibialis anterior (TA), tibialis posterior (TP), peroneal longus (PL), and peroneal brevis (PB) muscles using SWE.

METHODS

A total of 109 recreationally active healthy adults participated. The study employed a single-cohort, same-day repeated-measures test-retest design. Elasticity, measured in kilopascals as the Young's modulus, was converted to the shear modulus. All four muscles were measured in NWB and at 90% WB.

RESULTS

Intra-rater reliability estimates were good to excellent for NWB (ICC = 0.930-0.988) and WB (ICC = 0.877-0.978) measures. Inter-rater reliability estimates were moderate to good (ICC = 0.500-0.795) for NWB measures and poor to good (ICC = 0.346-0.910) for WB measures.

CONCLUSION

Despite the studies poor to good inter-rater variability, the intra-rater reproducibility represents the potential benefit of SWE in NWB and WB. Establishing the reliability of SWE with clinical and biomechanical approaches may aid in improved understanding of the mechanical properties of muscle.

Comparison between Exercise Program-Foot Orthoses Treatment and Exercise Program Alone after Pilon Fracture Surgery: Study Protocol for a Randomized Controlled Trial

The management of tibial pilon fractures is challenging and often leads to complications and limitations in ankle function. The study aims to investigate myotonometric parameters and muscle strength of ankle muscles, as well as gait pattern and balance among patients following surgical treatment of pilon fractures. The randomized controlled study will analyze the differences between the patients who will follow a 3-month physical exercise program and will wear customized foot orthoses (i.e., customized orthotic arch support insoles) versus patients who will attend only the physical exercise program. For each group, at least 21 patients will be required. The assessment involves four different testing procedures: myotonometry (anterior tibialis, medial and lateral gastrocnemius, and longus peroneus assessed using MyotonPRO), muscle strength testing (ankle dorsiflexors, plantar flexors, and peroneal muscles assessed using MicroFET2 dynamometer), analysis of gait parameters (using Scheinworks treadmill), and double-leg and single-leg balance tests (using K-Force plate). After 3 months, the assessments will record which of the two treatments (physical exercise program with or without wearing customized foot orthoses) has better outcomes in regaining ankle muscle properties and tone, as well as the restoration of gait and balance.

Impact of lower muscle stiffness on ankle dorsiflexion restriction in children with cerebral palsy evaluated using ultrasound elastography

BACKGROUND

Plantar flexor muscles always contribute to limiting the range of motion of ankle dorsiflexion in children with spastic cerebral palsy, but the individual contributions of these muscles are not well defined. This study aimed to identify which muscles' stiffness impacts the dorsiflexion range of motion in children with cerebral palsy.

METHODS

Twenty-five children with cerebral palsy were included. The maximum passive dorsiflexion range of motion was measured in two positions: hip and knee joints in flexion, and both joints in full extension. Strain ratios indicating muscle stiffness were measured using strain elastography of the lateral and medial gastrocnemius, soleus, flexor hallucis longus, peroneus longus, peroneus brevis, and tibialis posterior muscles. To analyze which muscles impact the limitation of the dorsiflexion range, multiple regression analyses were conducted. The values of muscle stiffness were included as independent valuables, and the values of the dorsiflexion range were included as dependent valuables. A p-value <0.05 was considered statistically significant.

FINDINGS

In the analyses, the soleus and flexor hallucis longus muscle stiffness were significant independent factors for the dorsiflexion range of motion of hip and knee flexion (adjusted R2: 0.50). The lateral gastrocnemius muscle stiffness was a significant independent factor for the dorsiflexion range of motion with both joints in full extension (adjusted R2: 0.61).

INTERPRETATION

Flexor hallucis longus muscle stiffness, in addition to triceps surae muscle stiffness, was shown to impact dorsiflexion range; attention should be paid to muscle stiffness in children with cerebral palsy.

Changes in echo intensity of the gastrocnemius muscle with passive ankle dorsiflexion: can echo intensity be used to assess muscle elongation?

Introduction: While shear modulus has been used as an index of muscle elongation, high costs prevent its general adoption. A more general indicator that can quantify muscle elongation non-invasively is needed to develop effective methods for stretching each muscle. The purpose of this study was to determine whether the echo intensity of the muscle changes with muscle elongation compared with the shear modulus. Methods: Sixteen healthy males (24.1 ± 2.8 years) participated in the study. Shear modulus and echo intensity of the medial gastrocnemius were assessed at 20° and 10° of ankle plantar-flexion, and 0°, 10°, and 20° of ankle dorsiflexion (presented as -20°, -10°, and 0°, +10°, +20°, respectively). Shear modulus was measured using ultrasound shear wave elastography. The echo intensity was quantified using the average grayscale value of a given region of interest (RoI) in longitudinal and transverse B-mode images. Grayscale analysis was performed using two RoIs: one which included as much of the muscle as possible (maximum RoI), and a rectangular one whose size and depth was identical for all images (rectangular RoI). Pearson's correlation coefficients between either the shear modulus or echo intensity and the ankle angle and between the echo intensity and shear modulus were calculated separately for each participant. Results: Average Pearson's correlation coefficient between shear modulus and ankle angle of the participants was 0.904. The average Pearson's correlation coefficients between the echo intensity and ankle angle were estimated to be 0.797 and 0.222 for the maximum RoI and 0.698 and 0.323 for the rectangular RoI in the longitudinal and transverse images, respectively. The average Pearson's correlation coefficients between the echo intensity and shear modulus were 0.684 and 0.514 for the maximum RoI, and 0.611 and 0.409 for rectangular RoI in the longitudinal and transverse images, respectively. Discussion: The results indicate that the echo intensity in the longitudinal image of the gastrocnemius, especially when assessed using the maximum RoI, increased with muscle elongation by passive ankle dorsiflexion. Therefore, assessment of the echo intensity using the maximum RoI in the longitudinal image might be useful for quantifying the muscle elongation.

Shear wave imaging the active constitutive parameters of living muscles

Shear wave elastography (SWE) of human skeletal muscles allows for measurement of muscle elastic properties in vivo and has important applications in sports medicine and for the diagnosis and treatment of muscle-related diseases. Existing methods of SWE for skeletal muscles rely on the passive constitutive theory and have so far been unable to provide constitutive parameters describing muscle active behavior. In the present paper, we overcome this limitation by proposing a SWE method for quantitative inference of active constitutive parameters of skeletal muscles in vivo. To this end, we investigate the wave motion in a skeletal muscle described by a constitutive model in which muscle active behavior has been defined by an active parameter. An analytical solution relating shear wave velocities to both passive and active material parameters of muscles is derived, based upon which an inverse approach has been developed to evaluate these parameters. To demonstrate the usefulness of the reported method, in vivo experiments were carried out on 10 volunteers to obtain constitutive parameters, particularly those describing active deformation behaviors of living muscles. The results reveal that the active material parameter of skeletal muscles varies with warm-up, fatigue and rest. STATEMENT OF SIGNIFICANCE: Existing shear wave elastography methods are limited to imaging the passive parameters of muscles. This limitation is addressed in the present paper by developing a method to image the active constitutive parameter of living muscles using shear waves. We derived an analytical solution demonstrating the relationship between constitutive parameters of living muscles and shear waves. Relying on the analytical solution, we proposed an inverse method to infer active parameter of skeletal muscles. We performed in vivo experiments to demonstrate the usefulness of the theory and method; the quantitative variation of the active parameter with muscle states such as warm-up, fatigue and rest has been reported for the first time.

Relationship between the Young's Modulus of the Achilles Tendon and Ankle Dorsiflexion Angle at Maximum Squat Depth in Healthy Young Males

Background and Objective: Achilles tendon (AT) stiffness can reduce ankle dorsiflexion. However, whether AT stiffness affects the ankle dorsiflexion angle at a maximum squat depth remains unclear. Therefore, we aimed to investigate the relationship between the Young's modulus of the AT and ankle dorsiflexion angle at the maximum squat depth in healthy young males using shear-wave elastography (SWE). Materials and Methods: This cross-sectional study included 31 healthy young males. AT stiffness was measured using the Young's modulus through SWE. The ankle dorsiflexion angle at the maximum squat depth was measured as the angle between the vertical line to the floor and the line connecting the fibula head and the lateral malleolus using a goniometer. Results: Multiple regression analysis identified the Young's modulus of the AT at 10° of ankle dorsiflexion (standardized partial regression coefficient [β] = -0.461; p = 0.007) and the ankle dorsiflexion angle in the flexed knee (β = 0.340; p = 0.041) as independent variables for the ankle dorsiflexion angle at maximum squat depth. Conclusions: The Young's modulus of the AT may affect the ankle dorsiflexion angle at the maximum squat depth in healthy young males. Therefore, improving the Young's modulus of the AT may help increase the ankle dorsiflexion angle at maximum squat depth.

Tibialis posterior muscle stiffness assessment in flat foot subjects by ultrasound based Shear-Wave Elastography

BACKGROUND

Few methodologies are used to assess Tibialis Posterior muscle stiffness. Those present limitations leading to a lack of evidence. Muscle stiffness assessment can help in the injuries risk factors identification while coupling with Ultrasound based Shear-Wave Elastography for its management. However, a precise and reliable methodology needs to be utilized to increase stiffness accuracy among the entire Tibialis Posterior muscle. Therefore, this study aims to investigate the stiffness association between Tibialis posterior deep and superficial layer and between flat and neutral footed subjects.

METHODS

The sample consisted of 18 participants, where 9 subjects represent the flatfoot group and 9 the neutral foot group. Only the subjects who presented a Navicular Drop Test value of > 9 mm were included in the flatfooted group. All participants were submitted to the Tibialis posterior stiffness assessment with the help of Ultrasound base Shear-Wave Elastography in a lying supine position. Association between Tibialis Posterior deep and superficial layers were determined by Pearson's correlation analysis and group differences were assessed using the U-Mann Whitney test in the comparison between flat foot and neutral foot group (p < 0.05).

RESULTS

No significant correlations between Tibialis Posterior layers stiffness were found (p = 0.194), nor in the comparison between both neutral and flat foot groups (p = 0.424/p = 0.258).

CONCLUSION

Among participants, no associations between tibialis posterior layers stiffness were found. Also, we did not find any differences in the stiffness between flat and neutral foot groups. In this study, the stiffness did not differentiate flat-footed subjects from neutral subjects.

An ex-vivo validation of the modulus-length framework to characterize passive elastic properties of skeletal muscle

The passive elastic properties of skeletal muscles are related closely to muscle extensibility and flexibility. Recently, a single probe setup has been reported that measures the passive elastic properties of muscles in vivo. This uses a modulus-length framework to investigate sensitive dynamic parameters, termed as passive elastic coefficient k, slack length l₀, and slack shear modulus G₀ to quantify the passive elastic properties of human muscle. In particular, the parameter k calculated based on this framework reflects the change rate of the local shear modulus with respect to the muscle length, which remains constant during the entire passive stretching process. In this report, the modulus-length framework was validated in four groups of ex-vivo muscle samples (young and old chickens, pork, and beef). All the muscle samples were stretched mechanically whilst muscle length was monitored and recorded with simultaneous measurement of dynamic shear wave elastography (SWE). Agreement analyses using Bland-Altman diagrams and intraclass correlation coefficients (ICC) were then performed on coefficient k values obtained by mechanical stretching (k1) and real-time ultrasound imaging methods (k2). Bland-Altman diagrams show that the majority of the points lie within the 95 % LoA ([-1.87, 2.29]; p = 0.276) and the level of reliability was "good" to "excellent" based on the ICC results (ICC, 0.904; 95 % confidence interval, 0.813-0.953). This indicated that the ultrasound and mechanical methods produced very similar results. Meanwhile, the range of the coefficient k values in four muscle types and groups was significantly different (p < 0.05), a finding which strongly supports the potential use of this coefficient to characterize muscle quality and status.

Shear wave elastography characterizes passive and active mechanical properties of biceps brachii muscle in vivo

Mechanical characterization of individual muscles in their in vivo environment is not well studied. Shear wave elastography (SWE) as a non-invasive technique was shown to be promising in quantifying the local mechanical properties of skeletal muscles. This study aimed to investigate the mechanics of the biceps brachii muscle (BB) derived from SWE in relation to elbow joint position and contraction intensity during isometric contraction. 14 healthy, young subjects participated in the study and five different joint positions (60°-180° elbow angle) were investigated. Shear elastic modulus and surface electromyography (sEMG) of the BB and elbow torque were measured simultaneously, both in passive (i.e., resting) and active states during slow, sub-maximal isometric ramp contractions up to 25%, 50%, and 75% of the maximum voluntary contraction. At passive state, the shear elastic modulus of the BB increased with increasing elbow angle (p < 0.001). Maximum elbow flexion torque was produced at 60° and it decreased with increasing elbow angle (p = 0.001). During sub-maximal contractions, both elbow angle (p < 0.001) and contraction intensity (p < 0.001) had significant effects on the shear elastic modulus but only contraction intensity (p < 0.001) affected sEMG amplitude of the BB. Although torque was decreased at extended elbow positions (150°, 180°), higher active shear elastic modulus of BB muscle was found compared to flexed positions (60°, 90°). Linear regression of the BB sEMG amplitude over elbow torque showed good agreement for all joint positions (R² between 0.69 and 0.89) while the linear agreement between shear elastic modulus of BB and elbow torque differed between flexed (R² = 0.70 at 60° and R² = 0.79 at 90°) and extended positions (with the lowest R² = 0.57 at 150°). We conclude that using SWE, we can detect length-dependent mechanical changes of BB both in passive and active states. More importantly, SWE can be used to characterize active muscle properties in vivo. The present findings have critical importance for developing muscle stiffness as a measure of individual muscle force to validate muscle models and using SWE in clinical diagnostics.

Comparison Between Foam Rolling With and Without Vibration on Passive and Active Plantar Flexor Muscle Properties

Although foam rolling interventions with and without vibration have been used to increase flexibility in the field of sports, their effects on passive and active properties remain unclear. Hence, this study aimed to investigate the effects of foam rolling interventions on range of motion (ROM), shear elastic modulus, plantar flexor muscle strength, and jump performance. This randomized, controlled, crossover study included 16 healthy male participants who visited the laboratory three times (control condition, foam rolling condition, and vibration foam rolling condition), each with an interval of >72 h. In both foam rolling and vibration foam rolling conditions, participants were instructed to perform 60-s bouts of intervention for three sets, with 30-s rest between each set. In the vibration foam rolling condition, the intensity of vibration was set at a frequency of 48 Hz. Dorsiflexion (DF) ROM, shear elastic modulus, plantar flexor muscle strength, and drop jump height were determined before and after the rolling intervention. Our results showed a similar increase in DF ROM (p < 0.01, d = 0.51; p < 0.01, d = 0.65, respectively) and passive torque at DF ROM (p = 0.02, d = 0.51 and p < 0.01, d = 0.65, respectively) after foam rolling and vibration foam rolling. Medial gastrocnemius shear elastic modulus decreased only after vibration foam rolling (p < 0.01, d = 0.44). No significant main effects of time were observed in maximal voluntary isometric contraction torque (F = 2.0, p = 0.15, η_p² = 0.119) and drop jump height (F = 1.5, p = 0.24, η_p² = 0.091) after both interventions. Maximal voluntary concentric contraction torque showed a significant main effect of time (F = 7.59, p = 0.02, η_p² = 0.336). However, only after foam rolling, the maximal voluntary concentric contraction torque significantly decreased (p = 0.01, d = 0.39). Our results suggest that vibration foam rolling effectively alters passive muscle properties without decreasing muscle strength and performance.

Effects of a 9-weeks arch support intervention on foot morphology in young soccer players: a crossover study

Background

A flat foot is a common cause of chronic sports injuries and therefore many opportunities for arch support interventions exist. However, young athletes change their foot morphology due to developmental influences even without intervention. Therefore, developmental influences need to be considered when examining the effects of arch support, but there have not been sufficient longitudinal studies to date. This study aimed to determine the effect of the arch support intervention by performing a 9-weeks arch support intervention on the foot morphology and cross-sectional area of the foot muscles in flat-footed young athletes. Thirty-one elementary school boys (Age 11.4 ± 0.5 years, Height 145.2 ± 7.4 cm, Weight 38.8 ± 8.3 kg, BMI 18.2 ± 2.2 kg/m²) with a decreased medial longitudinal arch in the foot posture index were selected as participants from a local soccer club and randomly divided into two groups.

Methods

In one group, in the intervention period, an existing arch supporter was used to provide arch support, while in the other group, no special intervention was provided in the observation period. To account for developmental effects, the intervention study was conducted as an 18-weeks crossover study in which the intervention and observational phases were switched at 9 weeks after the intervention. Foot morphology was assessed using a three-dimensional foot measuring machine, and the cross-sectional area (CSA) of the internal and external muscles of the foot was assessed using an ultrasound imaging device. We examined the effect of the intervention by comparing the amount of change in the measurement results between the intervention and observation periods using corresponding t-tests and Wilcoxon signed-rank sum test, analysis of covariance methods.

Results

After adapting the exclusion criteria, 14 patients (28 feet) were included in the final analysis. The CSA of the abductor hallucis muscle (ABH) increased 9.7% during the intervention period and 3.0% during the observation period (p = 0.01). The CSA of the flexor digitorum longus muscle (FDL) increased 7.7% during the intervention period and 4.2% during the observation period (p = 0.02).

Conclusion

A 9-weeks arch supporter intervention may promote the development of the ABH and FDL CSA in young flat-footed soccer players.

Reliability of shear wave elastography for the assessment of gastrocnemius fascia elasticity in healthy individual

The mechanical properties of the deep fascia, particularly their stiffness, strongly affect the development of muscle pathologies (such as compartment syndrome) and the action of the muscles. However, the mechanical characteristics of the deep muscular fascia are still not clearly understood. The present study focuses on examining the reliability of ultrasonic shear wave elastography (USWE) devices in quantifying the shear modulus of the gastrocnemius fascia in healthy individuals, particularly their ability to measure the shear modulus of the deep fascia of the gastrocnemius during ankle dorsiflexion. Twenty-one healthy males (age: 21.48 ± 1.17 years) participated in the study. Using USWE, the shear moduli of the medial gastrocnemius fascia (MGF) and lateral gastrocnemius fascia (LGF) were quantified at different angles during passive lengthening. The two operators took turns measuring each subject's MGF and LGF over a 1-h period, and operator B took an additional measurement 2 h later. For the intra-operator test, the same subjects were measured again at the same time of day 5 days later. Both the intrarater [intraclass correlation coefficient (ICC) = 0.846-0.965)] and interrater (ICC = 0.877-0.961) reliability values for measuring the shear moduli of the MGF and LGF were rated as excellent; the standard error of the mean (SEM) was 3.49 kPa, and the minimal detectable change (MDC) was 9.68 kPa. Regardless of the ankle angle, the shear moduli of the LGF were significantly greater than that of the MGF (p < 0.001). Significant increases in the shear moduli of both the MGF and the LGF were observed in the neutral position compared to the relaxed position. These results indicate that USWE is a reliable technique to assess the shear modulus of the gastrocnemius fascia and detect its dynamic changes during ankle dorsiflexion. USWE can be used for biomechanical studies and intervention experiments concerning the deep fascia.

Is there a correlation between the femoral anteversion angle and the elasticity of the hip muscles in cases of intoeing gait due to increased femoral anteversion angle?

Purpose

One of the common causes of gait disturbance in children is increased femoral anteversion. There are not enough publications in the literature on muscles related to the hip joint in increased femoral anteversion. The aim of this study was to evaluate the relationship between the femoral anteversion angle and hip muscle elasticity in children walking inward, using shear wave elastography (SWE).

Material and methods

Seventeen children with bilateral increased femoral anteversion angle in computed tomography were prospectively included in this study. Elasticity values of the hip muscles (adductor magnus (adductor), iliopsoas (flexor), gluteus medius (abductor), gluteus maximus (extensor) muscles) were evaluated by ultrasound elastography by two observers. Quantitative measurements of the shear wave velocities were performed using virtual touch tissue imaging quantification.

Results

There was excellent harmony between the femoral anteversion angle measurements performed by the two observers and a good congruence between the muscle elastography evaluations. While there was a moderate significant correlation between the femoral anteversion angle and the elasticity values of the iliopsoas and adductor magnus muscles, no significant correlation was found with other muscle elasticity measurements.

Conclusion

Iliopsoas muscle and adductor magnus muscle elasticity are correlated with the femoral anteversion angle. With further studies, we think that physical therapy methods for the elasticity of the muscles associated with the femoral anteversion angle can reduce the complaints of the patients.

Effect of shod and barefoot running on muscle mechanical properties

BACKGROUND

Barefoot runners have a higher probability of lower leg and foot disorders compared to runners wearing traditional running shoes. However, the site of muscle stress due to barefoot running has not been reported. This study aimed to investigate the effects of shod and barefoot running on muscle mechanical properties.

METHODS

A total of 18 healthy male subjects were included in this study and were assigned to either the shod running group or the barefoot running group. While the shod group ran on the treadmill at a speed of 75% heart rate reserve for 45 min with shoes, the barefoot group ran without shoes after warm up session. As an index of muscle stiffness, the shear wave velocity (SWV) of the eleven lower extremity muscles were measured at rest before and after exercise using shear wave elastography.

RESULTS

The tibialis posterior SWV was increased after running in the shod (3.67 ± 0.41 m/s to 3.90 ± 0.45 m/s) and barefoot (3.70 ± 0.36 m/s to 4.02 ± 0.54 m/s) groups. In contrast, the vastus lateralis SWV was increased only in the shod group (2.62 ± 0.32 m/s to 2.80 ± 0.34 m/s), while the peroneus muscle SWV increased only in the barefoot group (3.24 ± 0.48 m/s to 3.50 ± 0.55 m/s and 2.92 ± 0.5 m/s to 3.11 ± 0.49 m/s for the superficial and deep layers, respectively).

CONCLUSIONS

The shod condition selectively influences changes in the stiffness of the vastus lateralis and peroneus muscles during running but has no effect on the tibialis posterior.

Effect of Resonant Frequency Vibration on Delayed Onset Muscle Soreness and Resulting Stiffness as Measured by Shear-Wave Elastography

This study utilized resonant frequency vibration to the upper body to determine changes in pain, stiffness and isometric strength of the biceps brachii after eccentric damage. Thirty-one participants without recent resistance training were randomized into three groups: a Control (C) group and two eccentric exercise groups (No vibration (NV) and Vibration (V)). After muscle damage, participants in the V group received upper body vibration (UBV) therapy for 5 min on days 1-4. All participants completed a visual analog scale (VAS), maximum voluntary isometric contraction (MVIC), and shear wave elastography (SWE) of the bicep at baseline (pre-exercise), 24 h, 48 h, and 1-week post exercise. There was a significant difference between V and NV at 24 h for VAS (p = 0.0051), at 24 h and 1-week for MVIC (p = 0.0017 and p = 0.0016, respectively). There was a significant decrease in SWE for the V group from 24-48 h (p = 0.0003), while there was no significant change in the NV group (p = 0.9341). The use of UBV resonant vibration decreased MVIC decrement and reduced VAS pain ratings at 24 h post eccentric damage. SWE was strongly negatively correlated with MVIC and may function as a predictor of intrinsic muscle state in the time course of recovery of the biceps brachii.

A profile of reference data for shear modulus for lower limb muscles in typically developing children

BACKGROUND

Shear wave elastography can measure shear wave speed in muscles, which is used to estimate shear modulus. Normative values and standardized methodology are needed for children. Study aims were to: estimate shear modulus behavior of lower limb muscles of typically developing children; and establish a profile of reference data and recommendations for clinical assessment.

METHODS

Forty-one typically developing children (mean 9.7 y, SD 1.9 y) completed assessment of resting shear modulus of rectus femoris, biceps femoris, gastrocnemius lateralis and tibialis anterior at short and long lengths using shear wave elastography. Effects of muscle length, age, sex and BMI were examined. Then, our data and data from a scoping review for typical individuals were collated according to Net-Longitudinal Tension Angle (net proximal and distal joint angles).

FINDINGS

Shear modulus was: higher at long versus short muscle lengths for all four muscles (P < 0.001); correlated with increasing age for tibialis anterior at short (r = 0.39) and long lengths (r = 0.42) (both P = 0.01); but not related to sex or BMI. Shear modulus: tended to increase with increasing Net-Longitudinal Tension Angle for 18 lower limb muscles; and was higher for children than adults for some muscles (e.g. tibialis anterior and gastrocnemius lateralis, both P < 0.001).

INTERPRETATION

In typically developing children, shear modulus of lower limb muscles increases with increasing Net-Longitudinal Tension Angle. Recommendations enable comparison of values across different test positions and populations. Some relation between shear modulus and age was identified, but more research is needed.

Ultrasonographic test for detecting the chiasma plantare formation between the flexor hallucis longus and flexor digitorum longus

PURPOSE

Flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are frequently used in surgery. Therefore, it is necessary to evaluate the chiasma plantare formation preoperatively. The development of ultrasonography (US) may help the chiasma plantare formation evaluation. The purpose of this study is to prove the usefulness of the US method using cadavers.

METHODS

Eleven cases (twenty-two ankles) were obtained from Asian adult cadavers. At first, we evaluated and compared the chiasma plantare formation using US. Later, we evaluated that using the findings after dissection as type A (connection from FHL to FDL of the second toe), type B (connection from FHL to the second and third toes), type C (connection from FHL to the second through fourth toes), or type D (connection from FHL to all lesser toes).

RESULTS

Chiasma plantare formation was classified as types A and B in fifteen and seven ankles, respectively. After dissection, chiasma plantare formation was classified as types A, B, and C in fourteen, six, and two ankles, respectively. Therefore, there was an 86% similarity between the two methods.

CONCLUSIONS

Chiasma plantare formation can be reliably and noninvasively evaluated using US. This may be useful for preoperative rehabilitation or surgical procedure planning.

Objective Assessment of Regional Stiffness in Achilles Tendon in Different Ankle Joint Positions Using the MyotonPRO

BACKGROUND Achilles tendinopathy commonly occurs in specific regions of the tendon, and Achilles tendon stiffness can be related to local pathological changes in the tendon. The MyotonPRO is a new handheld device that conveniently assesses stiffness of muscles and tendons. This study aimed to 1) evaluate the intra- and inter-rater reliability of stiffness measurements of the Achilles tendon at different ankle positions, 2) investigate the modulation of stiffness at different ankle joint angles, and 3) examine the differences between 2 regions of Achilles tendon stiffness. MATERIAL AND METHODS Thirty healthy young adults (15 men and 15 women) participated in this study. The regional Achilles tendon stiffness at 0 cm (AT-0) and 6 cm (AT-6) above the tendon insertion were evaluated by the MyotonPRO in the neutral position and 10° dorsiflexion of the ankle joint. Measurements of stiffness were taken by 2 raters on the first day and 5 days later. The stiffness data were compared by repeated measures analysis of variance (ANOVA). RESULTS The intra- and inter-rater reliability of stiffness measurements at AT-0 and AT-6 for each ankle position were good (all intraclass correlation coefficients >0.84). A significant modulation of Achilles tendon stiffness was obtained at different ankle joint angles (P<0.05). Stiffness at AT-0 was higher than at AT-6 (P<0.05) in both positions. CONCLUSIONS These results suggest the MyotonPRO reliably assessed Achilles tendon stiffness and monitors its modulation, and tendon stiffness increased with ankle dorsiflexion. Stiffness was also nonuniform along the length of the tendon.

Can Static Stretching Reduce Stiffness of the Triceps Surae in Older Men?

Purpose

The purpose of this study was to investigate reductions of muscle stiffness induced by static stretching in older and younger men.

Methods

Twenty older (62–83 yr) and 20 younger (21–24 yr) men were recruited. Ankle dorsiflexion static stretching was consisted of 90 s × 5 repetitions. Before and after the stretching, the dorsiflexion range of motion (RoM), passive plantar flexion torque, and shear modulus (an index of stiffness) of the medial (MG) and lateral gastrocnemius and the soleus were measured.

Results

RoM, passive torque, and shear modulus of the triceps surae measured at the maximal dorsiflexion angle before stretching were significantly lower for the older group than the younger group. This suggests a weak stretching intensity for older compared with younger people. The stretching significantly improved RoM for both groups. For the older group, a significant reduction in passive torque was only observed at a 15° dorsiflexion angle, and the shear modulus was significantly decreased only for the distal region of MG. For the younger group, passive torque was significantly reduced for the entire RoM, and a significant decrease in shear modulus was found for the central and distal regions of MG and lateral gastrocnemius. A significant correlation between the muscle shear modulus measured at the maximal dorsiflexion angle before stretching and a stretching-induced decrease in muscle shear modulus was observed for older and younger participants. This indicates that the higher stretching intensity can reduce more muscle stiffness.

Conclusion

Static stretching can reduce muscle stiffness regardless of age, although the stretching effect on muscle stiffness was limited for older people. This might be due to a lower stretching intensity for older than younger people.

Reliability of Myotonometric Measurement of Stiffness in Patients with Spinal Cord Injury

BACKGROUND Contracture is related to modulation of passive stiffness in muscle and tendon after spinal cord injury (SCI). Current clinical assessments of stiffness in muscles and tendons are subjective in patients with spinal cord injury. We proposed a quantitative method to evaluate stiffness of the gastrocnemius and Achilles tendon (AT) with a portable device, the MyotonPRO. The purpose of this study was to investigate the intraoperator and interoperator reliability of the MyotonPRO when used in patients after spinal cord injury. MATERIAL AND METHODS Fourteen patients with SCI participated in this study. Gastrocnemius stiffness and AT stiffness were measured with the MyotonPRO. RESULTS In participants with SCI, the intraclass correlation coefficient (ICC) values for intraoperator and interoperator reliability of stiffness measurements in the gastrocnemius and AT were excellent (all ICC >0.87), with relatively low values for standard error measurement (SEM) and minimal detectable change (MDC). CONCLUSIONS Our findings suggest that use of the MyotonPRO is feasible for evaluating stiffness of the gastrocnemius and AT in the lower limbs of patients with spinal cord injury.

Hip position influences shear wave elastography measurements of the hamstring muscles in healthy subjects

Ultrasound shear wave elastography (SWE) has recently emerged as a non-invasive tool for assessing muscle stiffness. The majority of studies utilizing SWE have focused primarily on upper-extremity muscles, with little attention attributed to lower-extremity muscles. In addition, of the studies that have been published, various joint and muscle positions have been examined, rendering it difficult to compare results across studies. Thus, the purpose of this investigation was to examine lower extremity medial hamstring muscles (semitendinosus and semimembranosus) and to determine how hip position (0° versus 90°) and muscle position (knee flexed versus extended) impacted resulting shear modulus values. Ten subjects varying widely in age participated in this study, and their hamstring stiffness was assessed in four separate positions: seated with the knee flexed and extended, and lying prone with the knee flexed and extended. Higher shear modulus values were found at the group-level when participants were seated compared to prone (hip placed at 90° compared to 0°). In addition, higher values were also found when the knee was extended compared to flexed, but only when the hip was placed at 90° (not 0°). These results demonstrate that joint and muscle position, particularly when assessing the hamstrings, largely impact resulting shear modulus values. Therefore, joint and muscle position need to be systematically controlled for and reported when establishing normative ranges for shear modulus values across specific age groups. This will enable physicians to more precisely determine whether patients' shear modulus values indicate clinically meaningful differences in comparison to normative data.

Modulation in the elastic properties of gastrocnemius muscle heads in individuals with plantar fasciitis and its relationship with pain

The objectives of this study were (1) to investigate the passive stiffness of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) in patients with and without plantar fasciitis (PF), (2) to explore the correlation between gastrocnemius stiffness and plantar fascia thickness (PFT) as well as the intensity of pain in patients with PF, (3) to detect optimal cut-off points for stiffness of the MG and LG for identifying patients with PF. Forty patients (mean age = 51.1 years ± 12.9) participated in this study. The elastic properties of the MG and LG were quantified using shear wave elastography ultrasound. The thickness of the plantar fascia was measured by B-mode imaging. The intensity of pain was assessed using a visual analogue scale. The results showed that when the ankle was in the relaxed position, patients with PF had increased passive stiffness in the MG (P < 0.05) but not in the LG. Significant correlations were found between pain and the stiffness of the MG (middle, distal; all P-values < 0.05) and no correlation was observed between pain and PFT (P = 0.416). The initial cut-off point for the stiffness of the MG was 29.08 kPa when the ankle was in the relaxed position. The findings from the present study show that an increase in muscle stiffness is not the same in the individual muscles of the gastrocnemius muscle. Traditional treatment of the whole gastrocnemius muscle might not be targeted at the tight muscle.

Thickness, cross-sectional area, and stiffness of intrinsic foot muscles affect performance in single-leg stance balance tests in healthy sedentary young females

The purpose of this study was to investigate the effect of thickness, cross-sectional area and stiffness of intrinsic foot muscles on performance in single-leg stance balance tasks in healthy sedentary young females. This study included a total of 40 healthy sedentary young females between the ages of 19 and 35 years. Single-leg stance balance assessments were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). Performance in the single-leg stance balance tests was assessed using the overall stability index (OSI), mediolateral stability index (MLSI) and the anteroposterior stability index (APSI). Lower scores indicated better postural stability. Stiffness, thickness and cross-sectional area measurements of the abductor hallucis (AbH), flexor digitorum brevis (FDB) and flexor hallucis brevis (FHB) muscles were performed using an ultrasonography device. Larger AbH and FHB muscles were correlated with higher OSI, APSI, and MLSI (r = 0.31-0.46, p < 0.05), whereas larger FDB muscle was correlated with higher OSI and MLSI (r = 0.28-0.38, p < 0.05). Higher stiffness of the AbH and FHB muscles were correlated with lower OSI, APSI, and MLSI (r = -0.32 to 0.58, p < 0.05), but stiffness of the FDB muscle was not significantly correlated with OSI, APSI, and MLSI (r = 0.03-0.22, p ˃ 0.05). These results suggest that larger AbH, FDB and FHB muscles are related to reduced performance in single-leg stance balance tests, whereas higher AbH and FHB stiffness are related to better performance in single-leg stance balance tests in healthy sedentary young females.

Regional Elastic Properties of the Achilles Tendon Is Heterogeneously Influenced by Individual Muscle of the Gastrocnemius

Background

Anatomical studies and the mechanical property studies showed that there is a strong correlation between Achilles tendon (AT) elasticity and individual gastrocnemius muscle (the medial head of gastrocnemius (MG) and the lateral head of gastrocnemius (LG)) elasticity. Limited ankle dorsiflexion range of motion has been correlated with decreased flexibility of the MG/LG/AT complex. However, no studies have been conducted to examine the exact correlation between the Achilles tendon and the individual muscle of the gastrocnemius.

Purposes

The purposes of the present study were (1) to evaluate intra- and interoperator reliabilities of elastic property measurements in the gastrocnemius muscle-Achilles tendon complex by using the shear wave elastography (SWE) and (2) to examine the correlation between the regional elastic properties of the AT and the individual muscle of the gastrocnemius.

Methods

Twenty healthy subjects (mean age: 22.50 (3.02) years) were recruited in this study. The elastic properties of the AT and the individual muscle of the gastrocnemius were quantified using the SWE.

Findings

The SWE has comparatively high reliability in quantifying the elastic properties of the muscle-tendon range from good to excellent. The intraoperator ICC of the gastrocnemius muscle-Achilles tendon complex was 0.77 to 0.95, while the interoperator ICC was 0.76 to 0.94. The minimal detectable change (MDC) of the muscle was 1.72 kPa, while the AT was 32.90 kPa. A significant correlation was found between the elastic modulus of AT and the elastic modulus of the MG (r = 0.668 and p = 0.001 at the relaxing position and r = 0.481 and p = 0.032 at the neutral position).

Conclusions

The SWE has the potential to assess localized changes in muscle-tendon elastic properties, provide more intuitive relations between elastic properties of the muscle tendon and function, and evaluate the therapeutic effect of the muscle tendon. A significant correlation between the AT and the MG was found, and it may provide a new treatment idea (targeted to the tight muscle heads) for the clinical setting to treat subjects with AT disorders.

Effect of Rest Duration Between Static Stretching on Passive Stiffness of Medial Gastrocnemius Muscle In Vivo

CONTEXT

In clinical and sports settings, static stretching (SS) is usually performed to increase range of motion (ROM) and decrease passive muscle stiffness. Recently, the shear elastic modulus was measured by ultrasonic shear wave elastography as an index of muscle stiffness. Previous studies reported that the shear elastic modulus measured by ultrasound shear wave elastography decreased after SS, and the effects of SS on shear elastic modulus were likely affected by rest duration between sets of SS.

OBJECTIVE

To investigate the acute effects of SS with different rest durations on ROM and shear elastic modulus of gastrocnemius and to clarify whether the rest duration between sets of SS decreases the shear elastic modulus.

DESIGN

A randomized, repeated-measures experimental design.

SETTING

University laboratory.

PARTICIPANTS

Sixteen healthy males volunteered to participate in the study (age 21.3 [0.8] y; height 171.8 [5.1] cm; weight 63.1 [4.5] kg).

MAIN OUTCOME MEASURES

Each participant underwent 3 different rest interval durations during SS (ie, long rest duration: 90 s; normal rest duration: 30 s; and short rest duration: 10 s). This SS technique was repeated 10 times, thus lasting a total of 300 seconds with different rest durations in each protocol. The dorsiflexion ROM and shear elastic modulus were measured before and after SS.

RESULTS

Our results revealed that dorsiflexion ROM and shear elastic modulus were changed after 300-second SS; however, no effects of the rest duration between sets of SS were observed.

CONCLUSIONS

In terms of decreasing the shear elastic modulus, clinicians and coaches should not focus on the rest duration when SS intervention is performed.

Non-uniform Stiffness within Gastrocnemius-Achilles tendon Complex Observed after Static Stretching

Higher stiffness of the Achilles tendon (AT) and gastrocnemius have been found to be risk factors associated with Achilles tendinitis. Static stretching (SS) is one intervention that has been investigated to improve the flexibility and therefore reduce injury risk. Previous studies have investigated the acute effect of SS on one region for AT and gastrocnemius morphology and stiffness; however, there is a lack of knowledge about the effect of SS on other regions of the AT and gastrocnemius (e.g., proximal vs. distal, within gastrocnemius). The aims of the present study were: (1) to investigate the acute effects of SS on the shear modulus of the medial gastrocnemius muscles (MG) and lateral gastrocnemius muscles (LG) and AT for different regions; (2) to examine the differences in range of motion (ROM) before and after SS; and (3) to investigate the change of thickness of AT and fascicle length of MG and LG before and after SS. The stiffness of AT and the gastrocnemius, fascicle length of the muscles, thickness of the AT, and maximal ankle joint dorsiflexion angle were measured in thirty healthy subjects (15 males, 15 females) before(pre) and immediately after (post) 5-minute SS. Stretching effects are not homogeneous among different regions. After SS administration, the proximal, middle, and distal regions of MG stiffness decreased by 34.12%, 22.45%, and 25.27%, respectively (p = 0.000), and LG stiffness decreased by 37.71%, 30.47%, and 22.13%, respectively (p = 0.000), whereas AT stiffness increased by 25.73%, 17.01%, and 19.53%, respectively (p= 0.000). ROM of ankle joint increased by 8.02% (p=0.00). Nevertheless, there were no changes in the thickness of AT and fascicle length of the gastrocnemius. These results suggest that non-uniform behaviour is consistently present within the gastrocnemius and AT, and the gastrocnemius heterogeneity is reduced after SS. The stretching maneuver could be effective to increase the flexibility.

Shear Wave Elastography of the Lumbar Multifidus Muscle in Patients With Unilateral Lumbar Disk Herniation

OBJECTIVES

To assess lumbar multifidus muscle stiffness in patients with unilateral lumbar disk herniation (LDH) causing nerve root compression using shear wave elastography (SWE).

METHODS

Thirty-three patients with unilateral subarticular LDH (L3-L4, L4-L5, and L5-S1) causing nerve root compression, diagnosed by magnetic resonance imaging, were enrolled in the study. Exclusion criteria were bilateral or multilevel LDH confirmed on magnetic resonance imaging, bilateral leg symptoms, and patients with a history of any spinal operation, malignancy, trauma, infection, spondylolisthesis, severe lateral recess stenosis, spinal canal stenosis, and substantial comorbidities. Two observers separately evaluated the multifidus muscle using SWE. Shear wave elastographic examinations of the muscle were performed slightly below the herniation using the spinous process of the vertebra as a landmark. The stiffness of the muscle between affected and normal sides was compared. Moreover, the correlation between the stiffness and duration of the symptoms and the correlation between the stiffness and severity of the nerve compression were also calculated.

RESULTS

The mean stiffness values of the multifidus muscle on the affected side (mean ± SD: observer 1, 14.08 ± 3.57 kPa; observer 2, 13.70 ± 4.05 kPa) were significantly lower compared to the contralateral side (observer 1, 18.81 ± 3.95 kPa; observer 2, 18.28 ± 4.12 kPa; P < .001). The muscle stiffness had a moderate negative correlation with the duration of the symptoms and the severity of the nerve compression (observer 1, r = -0.535; observer 2, r = -0.458; P < .001).

CONCLUSIONS

The multifidus muscle on the ipsilateral side of the LDH showed reduced stiffness values, and stiffness values were negatively correlated with the disease duration and severity of the nerve compression. Further studies might reveal the potential role of SWE of the multifidus muscle in determining clinical outcomes and assessing effectiveness treatment in patients with LDH.

Menstrual cycle variation and gender difference in muscle stiffness of triceps surae

BACKGROUND

We aimed to investigate the menstrual cycle variation and the gender difference of the triceps surae muscle stiffness and passive stiffness of the ankle joint.

METHODS

The subjects of the study included 12 healthy young women and 12 healthy young men. Shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles were measured as an index of muscle stiffness using shear wave elastography. The passive stiffness of the ankle joint was calculated from passive torque when the ankle joint was passively dorsiflexed. Measurements were conducted in the follicular, ovulatory, and luteal phases to examine the menstrual cycle variation.

FINDINGS

There was no difference noted in the passive stiffness or triceps surae muscle stiffness for young women in the menstrual cycle. As for gender differences, passive stiffness in all menstrual phases in women was lower while the soleus muscle stiffness in women was higher, compared to that in men.

INTERPRETATION

Our findings suggest that passive stiffness and muscle stiffness did not differ in the menstrual cycle. In addition, the measured part of the soleus was more tensioned in women than in men.

Change in skeletal muscle stiffness after running competition is dependent on both running distance and recovery time: a pilot study

Long-distance running competitions impose a large amount of mechanical loading and strain leading to muscle edema and delayed onset muscle soreness (DOMS). Damage to various muscle fibers, metabolic impairments and fatigue have been linked to explain how DOMS impairs muscle function. Disruptions of muscle fiber during DOMS exacerbated by exercise have been shown to change muscle mechanical properties. The objective of this study is to quantify changes in mechanical properties of different muscles in the thigh and lower leg as function of running distance and time after competition. A custom implementation of Focused Comb-Push Ultrasound Shear Elastography (F-CUSE) method was used to evaluate shear modulus in runners before and after a race. Twenty-two healthy individuals (age: 23 ± 5 years) were recruited using convenience sampling and split into three race categories: short distance (nine subjects, 3–5 miles), middle distance (10 subjects, 10–13 miles), and long distance (three subjects, 26+ miles). Shear Wave Elastography (SWE) measurements were taken on both legs of each subject on the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), soleus, lateral gastrocnemius (LG), medial gastrocnemius (MG), biceps femoris (BF) and semitendinosus (ST) muscles. For statistical analyses, a linear mixed model was used, with recovery time and running distance as fixed variables, while shear modulus was used as the dependent variable. Recovery time had a significant effect on the soleus (p = 0.05), while running distance had considerable effect on the biceps femoris (p = 0.02), vastus lateralis (p < 0.01) and semitendinosus muscles (p = 0.02). Sixty-seven percent of muscles exhibited a decreasing stiffness trend from before competition to immediately after competition. The preliminary results suggest that SWE could potentially be used to quantify changes of muscle mechanical properties as a way for measuring recovery procedures for runners.

The effect of a running task on muscle shear elastic modulus of posterior lower leg

Background

Medial tibial stress syndrome (MTSS) is one of the most common causes of exercise-related leg pain in runners. Because stopping training due to pain from MTSS could decrease the athlete’s competitiveness, it is necessary to construct MTSS prevention and treatment programs. However, the effect of running, which is believed to cause MTSS, on shear elastic modulus of the posterior lower leg is unclear. Therefore, the purpose of this study was to investigate the effect of 30 min of running on shear elastic modulus of the posterior lower leg in healthy subjects.

Methods

Twenty healthy males volunteered to participate in this study (age, 20.9 ± 0.6 y; height, 169.6 ± 4.5 cm; weight, 62.6 ± 5.2 kg). The shear elastic modulus of the posterior lower leg was measured using ultrasonic shear wave elastography before and immediately after a 30-min running task.

Results

Shear elastic moduli of the flexor digitorum longus and tibialis posterior were significantly increased after 30 min running task. However, there were no significant changes in shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, peroneus longus and peroneus brevis.

Conclusion

The results suggested that the increases in shear elastic moduli of flexor digitorum longus and tibialis posterior after running could be a risk factor for running-related MTSS development.